Continuously variable vehicle transmissions are, for example, known from EP, A1, 0 451 887. Here, the rpms of the drive end (primary end) and the output end (secondary end) are measured by two rpm sensors for adjusting or shifting the transmission ratio. The transmission ratio which is to be adjusted or is adjusted is determined from these sensor signals.
A belt transmission, which is continuously adjustable with respect to its transmission ratio, having a drive end and output end is known from DE, A1, 44 11 628. The drive end and output end have at least one axially displaceable element which has essentially the form of a conical disc. The belt part is, in general, put in place as a band, preferably a thrust element band or a belt or a chain between disc pairs which define the drive end and the output end.
To control the slip of the belt part, the axial displacement of at least one of the axially displaceable elements as well as the rpms of the drive end and the output end are detected. The output signal of a single sensor is evaluated for the rpm detection of one of the two ends as well as for the detection of the axial displacement on this end.